Heat exchanger and method of manufacturing the same

ABSTRACT

A heat exchanger comprising a readily heat-conducting block of material having at least one chamber, a gas-permeable filling mass in said chamber, the mass consisting of particles of readily heat-conducting material sintered together with a layer of a readily heat-conducting material provided on an outer circumferential surface of the mass, and a soldered joint provided between the layer and the inner wall of the chamber in at least one zone extending throughout the circumference of the filling mass.

nited States Patent 9 Severijns Feb. 26, 1974 [54] HEAT EXCHANGER ANDMETHOD OF 3,195,621 7/1965 Van Geuns et a1. 165/10 MANUFACTURING THESAME 3,237,421 3/1966 Gifford t 165/10 X 3,306,353 2/1967 Bume 165/165 x[75] Inventor: Adrlanus Petrus Severuns, 3,407,615 10/1968 Klippingl65/l54 x Emmasingel, Eindhoven, 3,433,299 3/1969 Fleming 165/154 xNetherlands [73] Assignee: U.S. Philips Corporation, New a w Davis,

York Attorney, Agent, or FirmFrank R. Trifari [22] Filed: May 15, 1972[21] Appl. No.: 253,360

[57] ABSTRACT Related US. Application Data [63] Continuation of Ser. No.14,555, Feb 26, 1970, A heat exchanger comprising a readilyheataballdonedconducting block of material having at least one chamber,a gas-permeable filling mass in said cham- U.S. R, her, the massconsisting of particles of readily heat- 62/6, 138/38 conductingmaterial sintered together with a layer of a [5 i I readily heatconducting material provided on an Outer [58] Fleld of Search-M 165N641179; circumferential surface of the mass, and a soldered 29/1573; 62/6;138/38 joint provided between the layer and the inner wall of thechamber in at least one zone extending throughout References Clted thecircumference of the filling mass.

UNITED STATES PATENTS 2,893,702 7/1959 Richardson 165/165 X 6 Claims, 1Drawing Figure Pmmemwe w 3194,, 1 10 r INVENTOR. ADRIANUS P. SEVERIJNSAGENT HEAT EXCHANGER AND METHOD OF MANUFACTURING THE SAME This is acontinuation of application Ser. No. 14,555, filed Feb. 26, 1970, nowabandoned.

The invention relates to a heat exchanger which is particularly suitablefor use in the temperature range below 2 K and comprises a readilyheat-conducting block of material having at least one chamber containingat least one gas-permeable filler of particles ofa likewise readilyheat-conducting material which are sintered together, preferably thesame material as that of the block, each of the chambers comprising attheir oppositely located ends, connections with which they can beincorporated in ducts through which flows of helium can be conductedwhich exchange heat with each other.

Heat exchangers of the type described are known. They are used, forexample, in cooling devices in which He or a mixture of He and Hecirculates as a working medium between a cooled place (cooler) and aplace to be cooled. Such cooling devices are described in Dutch Pat.application No. 6,807,902 and in U.S. Pat. No. 3,376,712. In thesecooling devices the temperature of the place to be cooled lies below 1K. In these devices it is desirable to cool the flow of medium flowingto the place to be cooled in the counter-current heat exchange withmedium flowing away from the place to be cooled. For this purpose heatexchangers are used having a construction as described above, in whichthe filling mass is formed by sintered copper balls having a diameter ofapproximately 40 am and the surrounding block of material alsoconsistsof copper.

The very fine copper balls give a very large heatexchangingjsurface areawith the circulating helium so that a good heat transfer is ensuredbetween helium and the filling mass. For a satisfactory operation of theheat exchanger it is furthermore necessary that a good heat transfer isensured from the filling mass to the block of material. In order toachieve this it is known to sinter-the pre-sintered filling mass, afterplacing in the chamber, to the block under a compression pressure. Inthis case large difficulties occur. First of all, as a result of thesintering together of the copper b'alls, cracks nearly always occur inthe filling mass after sintering in the chamber, and furthermore theresistance to flow increases which disturbsthe satisfactory operation.Secondly, as a resultof the compression the end face of the filling massis more or less-squeezed so that the resistance to flow of the fillingmass increases considerably. Since a low resistance to flowof the heatexchangers is essentialfor a satisfactory operation of the coolingdevice, it will be obvious that increase of the resistance to flow isnot acceptable.

It is the objectof the invention to provide aheat exchanger of the abovedescribed type in whichthe said drawbacks are fully obviated.

For that purpose, the heatexcha'nger according to the invention ischaracterized in that the filling mass comprises at its circumferentialsurface a layer of a readily heat-conducting material provided thereon,preferably the same material as that of the'fillin'g mass and the blockof material, andis incorporated so as to fit in the relative chamber, asoldered jointbein'g'provided between the layer of material and the wallof the relative chamber in at least one zone extending throughout thecircumference of the filling mass.

Due to the atomic contact between the provided layer of material and thefilling mass, a good heat contact is ensured. As a result of thesoldered joint between the layer of material and the block of material,a good heat contact is obtained in this case also.

Since the filling mass, after placing in the chamber, is no longersintered, cracking of the filling mass does not occur either, and thehelium can nevertheless not flow between the block and the filling mass,since this is prevented on the one hand by the soldered joint and on theother hand by the layer of material. So this layer has both a heattransmitting function and a sealing function. The end faces of thefilling masses remain readily open (no increase of the resistance toflow) since this is no longer sintered in the chamber.

According to the invention, all the components of the heat exchanger arepreferably manufactured from the same material. The advantage of this isthat the thermal expansion and the shrinkage, respectively, is the samefor all the components so that few thermal stresses occur. Copper is avery suitable material for this purpose. In a further favorableembodiment the layer of material is provided on the filling masselectrolytically.

The invention furthermore relates to a method of manufacturing theabove-described heat exchanger. It is characterized in that a rod ofsintered material is turned down to a diameter which is smaller byapproximately 1 mm than that of a chamber in a block of a readilyheat-conducting material, after which the rod is providedelectrolytically with a layer of readily conducting material, the endsof the rod being then liberated from the deposited layer of material,the rod being then rinsed to remote acid and salt, the rod being turneddown to such a diameter that the filling mass sawn at the desirablelength fits in the chamber, at least one annular groove being providedin the wall of the chamber prior to placing the filling mass, asoldering ring being provided in said groove the assembly being heatedto above the melting temperature of the solder after placing the fillingmass, the open side of the chamber being then sealed by soldering acover.

In order that the invention may be readily carried into effect, oneembodiment of a heat exchanger will now be described in greater detail,by way of example, with reference to the accompanying drawing which isdiagrammatic and not drawn to scale.

This heat exchanger comprises a copper block 1 in which two chambers 2and 3 are recessed. In each of these chambers, filling masses 4 and 5,respectively, of sintered copper balls are accommodated, said fillingmasses comprising at their circumferential surface electrolyticallygrown layers 6 and 7, respectively, of copper. The layers 6 and 7,respectively, are soldered to the copper block 1, at the points 8,9 and10,11, respectively. Pipes l2 and 13 soldered in an aperture in theblock 1, communicate with the lower side of the chambers 2, 3 while theupper side of the chambers 2 and 3 is sealed by soldered covers 14 and15, respectively, in each of which a pipe 16 and 17, respectively issoldered. Thus pipes 12 and 16 (and also pipes 13 and 17) eachconstitute a pair of inlet-outlet means with a flow path defined betweenthem.

This heat exchanger is manufactured as follows:

A rod of sintered copper balls is first turned down to a diameter whichis smaller by approximately 1 mm than that of the chambers 2 and 3. Alayer of copper, slightly more than 0.5 mm thick, is depositedelectrolytically on said rod. At the ends of the rod, the depositedlayer is removed and the rod is then rinsed with alkali so as to removethe acid residues. Then it is rinsed with warm water so as to remove theformed salts, after which it is fired in a vacuum. Pieces whichcorrespond to the dimensions of the filling masses 4 and 5 are then cutfrom said rod. Said filling masses are turned down to such a diameter asto fit in the chambers 2 and 3. At the points 8,9 and 10,11,respectively, annular grooves are provided in the wall of the chambers 2and 3, in which grooves, rings of soldering material are laid, theserings as shown having thickness, t, substantially less than the length,L, of the filling mass in the direction of the flow path between theinlet and outlet pipes. The filling masses 4 and 5 are then placed inthe chambers. Heating to above the melting temperature of the solder isthen carried out so that the soldered joints are obtained at the points8, 9 and 10, 11 respectively. Simultaneously with this solderingoperation the pipes 12 and 13 can be soldered in the block 1. The covers14 and 15 with the pipes 16 and 17 are then soldered on the block 1.

in this manner a heat exchanger is obtained having a good thermalcontact between the filling mass 4, 5 and the layer 6,7; as well as agood thermal contact between the layer 6,7 and the block 1. Leakagebetween the filling mass and the block is not possible. The fillingmasses 4 and 5 have a low resistance to flow, since no sintering takesplace after the arrangement of the filling masses in their chambers.

What is claimed is:

l. A heat exchanger for use in a temperature range below 2 K,comprising, a block of readily-heatconducting material, the block havingat least one internal chamber defining inner walls, the chamber furtherhaving inlet and outlet means thus defining a flow path through saidchamber, a gas-permeable filling mass having an outer surface and formedof sintered particles of a readily-heat-conducting material, a layer ofreadily-heat-conducting material deposited on said outer surface of thefilling mass, said mass disposed within said flow path and constitutinga partition of predetermined length between the inlet and the outlet,with said layer on said mass being in direct heat exchange contact withsaid inner walls of the chamber, and a soldered junction between saidchamber walls and said layer on said filling mass, the junction defininga circumferential zone of smaller thickness in the flow path directionthan said length of the mass, sealing said mass to said chamber wallssuch that the inlet and outlet can communicate only through said mass.

2. A heat exchanger comprising a copper block having at least oneinternal chamber defining inner walls, and spaced apart inlet and outletducts thus defining a flow path through the chamber, a gas-permeablefilling mass defining an outer surface, the mass formed of sinteredcopper particles, a layer of electrolytically deposited copper on saidouter surface of said filling mass, said mass disposed within said flowpath and constituting a partition between the inlet and the outlet withsaid layer on said mass being in direct heat exchange contact with saidinner walls of the chamber, and a copper solder junction between saidchamber walls and said layer on said filling mass the junction defininga circumferential annular zone sealing said mass to said chamber wallssuch that the inlet and outlet can communicate only through said mass.

3. Apparatus according to claim 1 wherein said block has a secondchamber spaced from and similar to the first chamber.

4. Apparatus according to claim 1 wherein said layer is anelectrolytically deposited layer.

5. Apparatus according to claim 1 wherein said block, the filling mass,and said layer are all copper.

6. Apparatus according to claim 1 wherein said solder junction definesan annular ring defining a plane generally transverse to said flow path.

1. A heat exchanger for use in a temperature range below 2* K,comprising, a block of readily-heat-conducting material, the blockhaving at least one internal chamber defining inner walls, the chamberfurther having inlet and outlet means thus defining a flow path throughsaid chamber, a gas-permeable filling mass having an outer surface andformed of sintered particles of a readily-heat-conducting material, alayer of readily-heatconducting material deposited on said outer surfaceof the filling mass, said mass disposed within said flow path andconstituting a partition of predetermined length between the inlet andthe outlet, with said layer on said mass being in direct heat exchangecontact with said inner walls of the chamber, and a soldered junctionbetween said chamber walls and said layer on said filling mass, thejunction defining a circumferential zone of smaller thickness in theflow path direction than said length of the mass, sealing said mass tosaid chamber walls such that the inlet and outlet can communicate onlythrough said mass.
 2. A heat exchanger comprising a copper block havingat least one internal chamber defining inner walls, and spaced apartinlet and outlet ducts thus defining a flow path through the chamber, agas-permeable filling mass defining an outer surface, the mass formed ofsintered copper particles, a layer of electrolytically deposited copperon said outer surface of said filling mass, said mass disposed withinsaid flow path and constituting a partition between the inlet and theoutlet with said layer on said mass being in direct heat exchangecontact with said inner walls of the chamber, and a copper solderjunction between said chamber walls and said layer on said filling massthe junction defining a circumferential annular zone sealing said massto said chamber walls such that the inlet and outlet can communicateonly through said mass.
 3. Apparatus according to claim 1 wherein saidblock has a second chamber spaced from and similar to the first chamber.4. Apparatus according to claim 1 wherein said lAyer is anelectrolytically deposited layer.
 5. Apparatus according to claim 1wherein said block, the filling mass, and said layer are all copper. 6.Apparatus according to claim 1 wherein said solder junction defines anannular ring defining a plane generally transverse to said flow path.